The field of the invention is systems and methods for magnetic resonance imaging (“MRI”). More particularly, the invention relates to systems and methods for MRI near metallic implants or devices.
MRI soft-tissue contrast can add substantial diagnostic value when assessing the tissue envelope around metallic implants. For example, the U.S. Food and Drug Association (“FDA”) issued a recommendation for using MRI in imaging assessments of recently recalled total hip replacements. Despite this inherent utility, magnetic susceptibility artifacts generated by implants have historically limited MRI's practical clinical application in assessments of instrumented joints. In response to this clinical need, Three-Dimensional Multi-Spectral Imaging (“3D-MSI”) technology was developed by the MRI research community to reduce susceptibility artifacts due to implanted devices.
One 3D-MSI technology is known as MAVRIC (Multi-Acquisition Variable-Resonance Image Combination). MAVRIC uses 3D fast spin echo (“FSE”) pulse sequences specifically designed to minimize metallic artifacts around metallic prostheses.
In order to the address the substantial magnetic susceptibilities of large metallic implants such as hip implants, MAVRIC and other 3D-MSI techniques are designed to address “worst-case-scenario” imaging problems. These techniques acquire sections around the metal implant at discrete Larmor frequency offsets that account for the field perturbations. The sections are then combined to generate an image of the tissue surrounding the metal implant. Typically, such techniques may use at least twenty different sections, referred to as “spectral bins” or “frequency bins” to create a single image. Capturing these bins can sometimes take as long as ten minutes. A patient must remain still during the duration of the acquisition, which, as the acquisition becomes longer, can lead to blurred images resulting from patient movement.
There remains a need for a 3D-MSI technique that requires less scan time and, thus, reduces the risk for image blurring from subject motion. Such a method would also have the benefit of increased patient comfort because of the reduced duration of time the patient is required to be in the MRI scanner.